In your house, there is a hallway with a standard light in the ceiling and a switch on the wall, at one end of the hall. It is wired in the usual fashion:

Figure 1

Questions:

1. You decide to add a second switch at the other end of the hallway so that either switch can control the light — either switch can turn the light on if it is off, and off if it is on. (This is a common household configuration using what is called a "3-way" switch.) Show the wiring diagram.

2. What logic function does this arrangement demonstrate?

3. In the middle of the hallway, there is a doorway. When you enter the hall through this doorway, you can't control the light without walking to the end of the hallway. So you decide to add a third switch there so that any of the three switches will control the light. What kind of wiring and switch will accomplish this need?

Answer